The thermal evaporation of metallic melts includes a broad industrial application spectrum, which ranges from the manufacturing of functional coatings up to the material synthesis from the gaseous phase (S. Shah et al., “Evaporation: Processes, bulk micro-structures and mechanical properties”, in: “Handbook of Deposition Technologies for Films and Coatings”, ed. P. Martin, pp. 135-252, William Andrew, Oxford, 2010, ISBN 978-0-8155-2031-3).
By inductively heating the melt, temperatures larger than 2.000° C. can be obtained, cf. A. Kuzmichev, L. Tsybulsky, “Evaporators with Induction Heating and their Applications” in: “Advances in Induction and Microwave Heating of Mineral and Organic Materials”, ed. S. Grundas, pp. 269-302, InTec, Rijeka, Croatia, 2011, ISBN 978-953-307-522-8, wherein large evaporation rates can be achieved. Even with regard to metals having low vapour pressure, such as for example gallium, an efficient thermal evaporation can be guaranteed by inductive heating, see J. E. Mahan, “Physical Vapor Deposition of Thin Films”, pp. 143-144, Wiley, 2000, ISBN 0-471-33001-9.
Evaporation devices are predominantly employed under high vacuum conditions (S. Shah et al, l.c., A. Kuzmichev et al. (2011), l.c.), wherein the molecular flow represents the dominating transport mechanism for the evaporated species. In some methods for manufacturing compound semiconductors, the evaporation is carried out in a coarse vacuum and the transport is effected in the gaseous phase by convection and diffusion (cf.: Yu. A. Vodakov et al., “High Rate GaN Epitaxial Growth by Sublimations Sandwich Method”, J. Crys. Growth 183 (1998) 10; E. Berkman, PhD Thesis, North Carolina State University, 2005; M. Imade et al., Mat. Lett. 59 (2005) 4026; H. Wu et al., phys. Stat. sol. (c) 7 (2005) 2032; D. Siche et al., J. Crys. Growth 310 (2008) 916.
The inductor can directly be positioned at the melting crucible (cf.: I. Ames et al., “Crucible Type Evaporation Source for Aluminum”, Rev. Sci. Instr., 37 (1966) 1737; R. R. Phinney, D. C. Strippe, “Crucible for Evaporation of Metallic Film”, U.S. Pat. No. 4,791,261; A. Kuzmichev, L. Tsybulsky, “Evaporators with Induction Heating and their Applications”, Przeglad elektrotechniczny, 84 (2008) 32).
Criteria for the selection of susceptor substances are a high melting point, a high electrical conductivity, a high resistance regarding temperature changes and an inert characteristic with respect to the melt and with respect to the gaseous atmosphere present in the specific application. A preferred substance for a susceptor is graphite (R. R. Phinney et al., l.c.; A. Kuzmichev et al. (2008), l.c.), in some instances also conductive special-ceramics (I. Ames et al., l.c.) or molybdenum (R. R. Phinney et al., l.c.) are used.